Sound recording



June 7 1932. s BAGNQ 1,862,327

SOUND RECORDING Filed Jan. 18, 1930 -llllllJlIl';

INVENTO SAMUELMBA N0 ATTORNEY Patented June 7, 1932 UNITED STATES PATENTOFFICE SAMUEL M. BAG-NO, OF BRONX, NEW YORK, ASSIGNOR'TO RADIOCORPORATION OF AMERICA, A CORPORATION OF DIE]LAWAJRJZI SOUND RECORDINGApplication filed January 18, 1930. Serial No. 421,782

The object of this invention is to provide an improved method of soundrecording.

A further object of this invention is to provide an improved method ofrecording sound upon moving strips as in the production of talkingmotion pictures.

Another object of my invention is to produce a sound record, in whichthe average density is directly proportional to the sound intensity.

A further object of this invention is to record sound upon a moving filmas striations.

It is a more particular object of this in vention to record sound upon amoving film as striations of uniform density.

These and other objects of this invention will become apparent from thefollowing specification taken in connection with the appended drawing.

In accomplishing my invention, the sound being recorded is caused toproduce a fluctuating electric current in the usual manner, and afteramplification, the current is used to charge a condenser, whichcondenser, when it is fully charged, discharges through a neon tube. Theintensity and duration of the light from the tube is always the same.The

number of lines per unit length of film varies indirectly with theimpedance of the tube, as caused by the varying input. In other words,

the number of lines in the negative will be directly proportional to theintensity of the sound, and each line will be recorded to be equallyblack and will have the same width.

' Therefore, the average intensity of the light falling through thepositive upon the photocell in reproduction, will be directlyproportional to the number of lines upon the negative produced byrecording, in accordance in density in direct proportion to the-soundintensity.

Having thus briefly described my invention, attention is invited to theaccompanying drawing in which; i

Fig. 1 shows a diagram of a circuit adapted to produce a film record inaccordance with my invention; and,

Fig. 2 represents a section of the negative record as produced by myinvention.

Referring now more particularly to Fig. 1, the microphone for picking upthe'sounds to be recorded is represented at 11 and is connected throughthe source 12 to the primary 13 of the transformer 14. The secondary 15of the transformer 14 is connected to the input of the thermionic device16. I The filament of the thermionic device 16 is supplied by the lowpotential source 17 in the usual manner. 1 The plate circuit ofthethermionic device 16 includes the neon tube 18 and'the condenser 19 inparallel, and the high potential source 20. The light produced 'by theneon tube 18is adapted to be concentrated and focused upon the film as anarrow band of light running transverse the film record 22. i

The record 22 is adapted to be moved past the optical system 21 at auniform speed, the details of the mechanism for moving which constituteno part of the present invention. Referring now more particularly toFig.

2, there is. shown a section of the negative of the film 22 as producedby my invention. The sound strip is represented 'as 26 and is composedofa series of striations 27, the spacingof which will vary from theminimum spacing, as shown at 23 to the maximum spacing as shown at 24,the total record as shown .,in this figure being intended to represent aIn the positive, the sound would be composed of dense portions ofvarying length separatedby clear portions of the pure 'sine wave.

same width. -The operation of my recording arrangement is as follows:Thesound to be recorded is picked up by the microphone 11 and amplifiedby the amplifier device 16. The output of 16 serves to charge thecondenser 19, which latter may be of the order of .1 microfarad. As soonas this condenser has been charged to the break down voltage of the neontube 18, it Will be discharged, causing a light which will produce astriation upon the film 22. The duration of the light impulses aredetermined merely by the charge of the condenser 19, and will bepractically independent of the length of time necessary to charge thecondenser. Therefore. the duration of the light impulses will bepractically the same and the clear portions of the finished film will beof even Width. The length of time necessary to charge the condenser Willvary, of course, in accordance with the intensity of the current beingrecorded, and will be represented on the finished film as dark portionsof varying length.

Having thus described my invention, attention is invited .to .the factthat various modifications may be made difiering from the form shown anddescribed for the purpose of illustration only, but falling within thescope of my invention. I am, therefore, not to be limited to thespecific form shown but by the scope of my invention as set forth in theappended claims.

' '1 claim 1. The method of sound recording which comprises producing anelectric current varying in accordance with the sound to berecorded,producing light impulses of constant duration at .an -intervalvaried in accordance with the intensity of the current representing thesound .to be recorded and recording of said light impulses.

2, The method of sound recording which comprises producing an electriccurrent varying in accordance with the sound to be recorded, producinglight impulses of constant duration, and at an interval varied inaccordance with the intensity of the current representing the sound toberecorded, and photographically recording said light impulses.

3. Apparatus for recording sound which comprises means for producing acurrent representative of the sound being recorded, means for amplifyingsaid current, a condenser adapted to be charged by the amplifiedcurrent, a gas filled lamp adapted to be actuated by said condenser whencharged to apredetermined voltage, a moving photographic record, andmeans for focusing the i ght from said gas filled lamp upon said movingrecord whereby a record representative of the sound being recorded isproduced, composed of'striations of equal width and density as arated byan amount varying inversely with the intensity of the sound pulses beingrecorded.

4. Apparatus for recording sound which comprises a condenser adapted tobe charged by the current representative of the sound being recorded, aneon lamp adapted to be actuated by said condenser, and a movingphotographic record exposed to the light of said lamp, whereby a recordrepresentative of the sound being recorded is produced.

5. Apparatus for recording a current representative of the sound beingrecorded, which includes, a condenser adapted to be charged by saidcurrent, a light source adapted to be actuated by said condenser .and incircuit therewith, and a moving photographic record in cooperativerelation with the said light source upon which fluctuations of saidsource are recorded.

SAMUEL M. BAGNO.

